1. Technical Field
Some embodiments of the present invention(s) relate to power amplifiers, and more particularly, some embodiments relate to systems and methods for improved power amplifier performance.
2. Description of Related Art
Radio frequency (RF) power amplifiers and devices using Gallium Nitride (GaN) benefit over those using technologies such as gallium arsenide (GaAs). For example, GaN-based power amplifiers have exceptional power density (i.e., increased power per square millimeter of die) and exceptional power efficiency characteristics. Unfortunately, one of the challenges of using GaN-based power amplifiers is controlling the quiescent drain current (Iq) of such power amplifiers over time. FIG. 1 provides a chart depicting the drift of the quiescent drain current (Idq) of an example GaN power amplifier over time. Such drift impacts certain systems, because as the quiescent drain current (Idq) of a GaN power amplifier changes, so does the performance of the GaN power amplifier. One solution to this is a “burn-in” procedure, whereby a GaN power amplifier is energized until the quiescent drain current (Idq) of the GaN power amplifier stabilizes. The “burn-in” procedure is time consuming, it is difficult to tell how much time will be required for Idq stabilization in GaN power amplifiers (as it is difficult to predict the drift of the quiescent drain current over long periods of time), and a GaN power amplifier cannot be biased at a constant drain current for its drain current varies according with its RF power output.
Another issue affecting GaN amplifiers relates to their use in non-Class A applications. In particular, it has been observed that the drain current of a GaN amplifier changes dramatically with radio frequency (RF) power level changes when the GaN power amplifier is operating at a power level closer to its power compression point (Psat). As a result, when a GaN power amplifier is operating at a power level closer to its Psat, control of the drain current of the GaN amplifier with a closed-loop control is difficult, as a small error in the RF power level detected by a radio frequency (RF) power detector results in a large variation of the drain current.